In general, a quartz crystal resonator is housed in a quartz crystal unit and a quartz crystal oscillator comprises the quartz crystal unit. For example, a quartz crystal oscillator with a quartz crystal unit comprising a contour mode resonator such as a quartz crystal tuning fork resonator, which is capable of vibrating in a flexural mode, is widely used as a time standard in consumer products, wearable time-keeping equipment and communication equipment (such as cellular phones, wristwatches and pagers). Recently, because of high frequency stability, miniaturization and the light weight nature of these products, the need for a smaller quartz crystal unit and a smaller quartz crystal oscillator with a smaller quartz crystal tuning fork resonator, capable of vibrating in a flexural mode and having a high frequency stability, a small series resistance and a high quality factor has arisen.
Heretofore, however, it has been impossible to obtain a quartz crystal unit and a quartz crystal oscillator because a conventional quartz crystal tuning fork resonator, capable of vibrating in a flexural mode can not be obtained with a high frequency stability, a small series resistance and a high quality factor when it is miniaturized.
Moreover, nothing teaches figure of merit M of the present invention which has an influence on a frequency stability for a flexural mode, quartz crystal tuning fork resonator capable of vibrating in a fundamental mode and teaches a relationship of an amplification circuit and a feedback circuit which construct a quartz crystal oscillating circuit of the present invention, and also, nothing teaches a method of manufacturing a quartz crystal tuning fork resonator capable of vibrating in a flexural mode, a quartz crystal unit and a quartz crystal oscillator of the present invention.
Likewise, nothing teaches a method for manufacturing a quartz crystal unit comprising a contour mode resonator such as a width-extensional mode quartz crystal resonator, a length-extensional mode quartz crystal resonator and a Lame mode quartz crystal resonator, and their resonators, according to the present invention.
In addition, for example, there been has a big problem in the conventional quartz crystal oscillator with the conventional quartz crystal tuning fork resonator, such that a fundamental mode vibration of the resonator jumps to a second overtone mode vibration by shock or vibration.
It is, therefore, a general object of the present invention to provide embodiments of a contour mode resonator such as a flexural mode, quartz crystal tuning fork resonator, a width-extensional mode quartz crystal resonator, a length-extensional mode quartz crystal resonator and a Lame mode quartz crystal resonator, a quartz crystal unit with the contour mode resonator and a quartz crystal oscillator comprising a quartz crystal oscillating circuit with a flexural mode, quartz crystal tuning fork resonator, capable of vibrating in a fundamental mode, and having a high frequency stability, a small series resistance and a high quality factor, and also to provide embodiments of a method for manufacturing the contour mode resonator, the quartz crystal unit and the quartz crystal oscillator, which overcome or at least mitigate one or more of the above problems.